1. Technical Field
The present invention relates to integrated circuit devices in general, and, in particular, to integrated circuit devices having a real-time clock oscillator. Still more particularly, the present invention relates to an apparatus for controlling power to a real-time clock oscillator within an integrated circuit device.
2. Description of the Related Art
A real-time clock oscillator within an integrated circuit device typically receive its power from a battery external to the integrated circuit device. Since the battery has a limited lifetime, it is crucial for the real-time clock oscillator to draw a minimal amount of current in order to preserve the life of the battery.
Referring now to the drawings and in particular to FIG. 1, there is depicted a circuit diagram of a real-time clock oscillator, according to the prior art. As shown, a real-time clock oscillator 10 includes an inverting amplifier 11, a feedback resistor 12, a drive resistor 13, a crystal 14 and capacitors 15-16. Inverting amplifier 11, feedback resistor 12, and drive resistor 13 are usually incorporated within an integrated circuit device (i.e., on-chip). On the other hand, crystal 14 and capacitors 15-16 are usually discrete devices external to the integrated circuit device (i.e., off-chip) and are mounted on a printed circuit board. The majority of the power consumed by oscillator circuit 10 is through inverting amplifier 11.
With reference now to FIG. 2, there is depicted a circuit diagram of inverting amplifier 11 according to the prior art. As shown, inverting amplifier 11 includes a p-channel transistor 21 and an n-channel transistor 22. Although transistors 21 and 22 are connected in an inverter configuration, transistors 21 and 22 operate largely in the saturation region throughout each oscillator cycle. Hence, the majority of the power dissipation of inverting amplifier 11 is attributed to shoot-through current from a power supply VDD passing through inverting amplifier 11 to ground.
The present disclosure provides a solution to minimize the DC current so that the power loss through an inverting amplifier within a real-time clock oscillator, such as inverting amplifier 11, can be minimized. As a result, the power consumption of the real-time clock oscillator can also be minimized.